Leadership does matter in politics. So does the underlying strategy. And it's fairly clear what Labour's chosen political direction is, regardless of which leadership contestant wins.

Labour has been torn between two strategic options. The all-important centre of New Zealand politics is the battleground for swing-votes. If a Labour-Green duo is to get the numbers to form a government, one option is for Labour to capture a greater share of those voters.

But the centre is getting crowded, with National, NZ First and now even the Greens taking slices of that part of the pie. (Don't believe John Key's hype about the Greens being "far left", because many of their voters are urban, educated and middle-income, and concern for the future of the planet is fairly mainstream now.)

Labour's other option is to go for those who may not vote at all. That sounds funny perhaps, but in 2011 the non-voters were about one third of those eligible.

That's enough to win an election, if only you can mobilise them. These people tend to be young, lower-income, and/or Maori or Pasifika. Many are those "left out" by the economic reforms of recent decades, and they've become politically disengaged. Their worries are likely to be a job, a wage and paying the rent. Saving the planet can wait for another day.

Addressing the needs of this constituency is socially responsible, and it could work for Labour electorally. The only real competition at that end of the political spectrum is the Mana Party which earned only 1 per cent of party votes in 2011. So it is a high-risk strategy for Labour, as Pasifika and Maori and unemployed youth may not vote at all, let alone for Labour.

That's where Shane Jones's candidacy for the Labour leadership makes sense. His participation will energise Maori members of the Labour Party. He will give Labour a push in the Maori electorates and among those whom he calls "the 800,000 lost tribe of voters". As I write this, Mr Jones is considered the least likely to win the Labour leadership, but nonetheless his candidacy is useful to Labour strategy.

Of all three candidates, David Cunliffe is best placed to appeal to voters in the centre. He has good experience as a Cabinet minister, and can tackle Key in the House. His background in business and economics is solid, and he enjoys a comfortable middle-class lifestyle.

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But Cunliffe has made it clear that the centre is not his target audience. His speech announcing his bid for the leadership emphasised the young and the vulnerable, and schools, hospitals and homes. This is solid Labour social democratic territory, and calls for strong state organisation and taxation. And he hinted that he'd lift the minimum wage.

But while Cunliffe has made a pitch to the left, his waspish look and policy-wonkish tone may not inspire the low-income constituency that Labour seeks to mobilise.

Grant Robertson is undoubtedly a strong performer too. He is capable of taking on Key in the House and he comes across extremely well in the media. He's electable, but relatively young and lacks ministerial experience. His appeal is more to the urban liberal-left - or those who probably vote Labour anyway.

Whichever leader it goes for, Labour is now pitching for the "unclaimed" disfranchised left. This leaves it open to Mr Key's barb that the election "will be a centre-right government of six years of proven quality, versus a kind of far-left opposition".

National must be happy Labour isn't contesting the centre this time around.

Winston Peters must be pleased too, because those who might have voted National but are too grumpy about their government will vote for him in protest rather than switch to Labour.

For every party vote that Labour fails to gain in the centre, it will have to mobilise two or more supporters in the likes of Mangere or Tamaki Makaurau to lift its polling out of the low 30s.

Labour's nightmares could return at the next election if, despite its best efforts, those low-income neighbourhoods just don't turn out to vote for Labour. They may not hear or believe the message about hope and equality, and they may not see Labour's leader as representing anything new or hopeful or relevant. Heavy rain on election day could be enough to tip the balance.

John Key has not yet reached that unhappy threshold where the factors that led middle New Zealanders to support him turn into reasons for no longer liking him.

So chances are we will see a National-NZ First government after the next election.

Dr Grant Duncan is an associate professor in the politics programme at Massey University's Albany campus.